This invention relates to tunable, all-fiber optical filters containing Fabry-Perot cavities formed in bare fiber, and that are thermally or electromechanically tunable. The invention is also directed to tunable filters comprising two or more of these tunable all-fiber Fabry-Perot filters (FFP component filters) which are optically coupled to achieve desirable properties.
Multiple-stage filters combining component filters of selected FSR to provide a vernier configuration are known in the art. See, for example, Oretag, B. et al. (July 1999) J. Lightwave Technology 17(7):1242–1244; Humblet, P. A.; Hamdy, W. M. (August, 1990) “Crosstalk analysis and filter optimization of single and double-cavity Fabry-Perot filters” IEEE Journal on Selected Areas in Communications 8(6):1095–1107; Lemieux, J.-F et al. (2000) “100 GHz frequency step-tunable hybrid laser based on a vernier effect between a Fabry-Perot cavity and a sampled fiber Bragg grating.” OSA Trends in Optics and Photonics. Advanced Semiconductor Lasers and their Applications Vol. 31, from the Topical Meeting (July 1999) p: 186–188 Editor(s): Hollberg, L. and Lang, R. J. Optical Soc. America, Washington, D.C., USA; Lemieux J-F. et al, (May 1999) “Step-tunable (100 GHz) hybrid laser based on Vernier effect between Fabry-Perot cavity and sampled fibre Bragg grating” Electronics Letters 35(11):904–906; Gehrsitz, S. et al. (August 1997) “Tandem triple-pass Fabry-Perot interferometer for applications in the near infrared” Applied Optics(36):5355–61; Ja, Y. H. (September 1995) “Optical vernier filter with fiber grating Fabry-Perot resonators” Applied Optics 3(7):6164–617; Kaminow, I. P et al. (1989) “A tunable Vernier fiber Fabry-Perot filter for FDM demultiplexing and detection” IEEE Photonics Technology Letters 1(1):24–26; Lindsay, S. M. et al. (1981) “Construction and alignment of a high performance multipass vernier tandem Fabry-Perot interferometer” Review of Scientific Instruments 52(10):1478–1486 and references cited therein.